Relationships Between U.S. Naval Observatory, Loran-C and the Defense Satellite Communication System

Laura G. Charron

Abstract:	Department of Defense (DoD) Directive 5160.51 of 31 August 1971 states that "All DoD components...refer time and time interval to the standards established by the (U.S. Naval) Observatory." To obtain the required traceability the most widely used system for timc dissemination has been the navigational system of the U.S. Coast Guard - Loran-C. When the only chain available for timing was the East Coast chain, monitored by the Observatory, there was no problem in publishing comparisons of that chain to the U.S. Naval Observatory's Master Clock (USNO MC) with a fair degree of reliability. By 1981, however, thirteen chains, covering a substantial portion of the Northern Hemisphere, were in use. The question of how the time comparisons were to be obtained, the chains calibrated, and the results published for chains not directly monitored by USNO then arose. During this same period, the number of 1 inks permitting time transfers point-to-point over the Defense Satellite Communication System (DSCS) were being expanded. In addition, at some selected sites, Loran-C monitoring equipment was installed. It was now possible to have values of USNO MC - DSCS Monitoring Site and thus to be able to determine USNO F1C minus Loran - C. This paper addresses, in general terms, the methods used in forming time scales for distant sites monitoring Loran-C. Particular emphasis will be given to the time transfers obtained via the DSCS and on how the data provided by this system is used to calibrate these remote time scales. The errors involved will be discussed.
Published in:	Proceedings of the 13th Annual Precise Time and Time Interval Systems and Applications Meeting December 1 - 3, 1981 Naval Research Laboratory Washington, DC
Pages:	201 - 216
Cite this article:	Charron, Laura G., "Relationships Between U.S. Naval Observatory, Loran-C and the Defense Satellite Communication System," Proceedings of the 13th Annual Precise Time and Time Interval Systems and Applications Meeting, Washington, DC, December 1981, pp. 201-216.
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